Method of neutralizing industrial waste



June 16, 1953` A. L. 'NuGEY Y 2,642,334

METHOD 0F NEUTRALIZING INDUSTRIAL WASTE Filed sept, 2o, 1947 SULFUR/c' y FERRol/.s- Vf IN VEN TOR. nwnyL JVzzgey.

Patented June 16, 1953 UNITED, STATES 'PATENT orties g n Merece or' runus'rmap WAS I Anthony L. ugey,Rahway, N.=J. y Application september 2o, 1947, serial Ngjvva'zol This'invention relates to the treatment` of yu ndesirable substances'that result from industrial processes -and have toxic orother deleterious characteristics; and more particularly to a proc-- ess or methodV of preventing the pollution of streams by extracting, "rec'overing'or converting injurious by-products -of industrial wastes..-r

An object of the invention is to facilitate the manufacture of compounds needed .in the -production of pigments-and to simplify lproblems in connection therewithfl l In this'eld white lead, zinc oxide,- lithopone, etcljhave long been recognized; and 'more'rec'ently titanium dioxide (TiO2) has come into Widespread' use because ithas more covering power due to its greater opacity.

This oxide is obtained from rutile and/ or ilmenite, which are the chiefsources for titaniumdioxide: (TiO'2); The latter is probably employed more extensively for this purpose.

Briefly, the ore is first ground and then digested in a'solution of strong sulphuric-acid (H2504), in the presence of water. When the reducing op- 3Clams. (01.23-63) eration hasfbeen completed, the. liquid is clarified,

vacuum evaporated, and filtered; and the resultant precipitate is dried, calcined, air-separated and finely pulverized and subsequently made up into marketable packages.

The liquid nitrate which is discharged from the several filtering and Aprecipitating operations has a specific gravity or' approximateiy 1.065` `(equal to 9 deg` B.) 'and'its Weight averages 8.87 lbs. per gallon. The analysis of this filtrate Will vary with the control of the processing operationsbut the average composition is:

81/2 H2SO4 (sulfuric acid) 11% FeSOiJTHzO (ferrous sulphate) 89% H2O (water) In previous attempts to recover the chemical compounds from the filtrate, the sulphuric acid (H2S04) and the iron (Fe) could not be converted into iron sulfide (FezS) as long as they are in solution. The ferrous sulphate (FeSO4-7I-I2O) is so soluble in the H2O (water) that it is necessary to make a 75 percent solution to get it saturated. Also it is not commercially feasible to extract the sulfuric acid (H2504), as such.

Another object of my invention is to provide Aa simple and commercially practical process for removing the chemical compounds in a continuous manner, and at the same time to overcome the present difficult problem of disposing of this very corrosive filtrate.

At present manufacturers of titanium dioxide beach front'. Y

('IiOz) oftenidisc-harge this nitrate into rivers and other streams as a Waste eiiiuent, but public authorities are adopting corrective measures to prohibit'the continuance of this practice. Some manufacturers with plants adjacent to seacoasts discharge this yhighly corrosive lfiltrate into the ocean. This is not only costly to `the manufacturer', who must provide suitable rubber lined vessels to transport this filtrate off-shore, but furtherentails great damage to fish and other mariney life, and is vaptjto ruiny long stretches of I' have lsuccessfully transformed the injurious contents of this nitrate into calcium ysulfate (CaSOrZI-Izo), or plaster of Paris (CaSOal/ZHzO) and iron oxide- (FegOs), bythe use of cheap chemical reagents land simultaneously neutralizedthe filtrate; thus rendering it harmless and permitting it to bedischarged freely without causing pollution of natural Waters. I also enable the manufacturer to save money and in addition in crease the proceeds of the methods heretofore utilized. y l

The nature and advantages of my invention will fullyfappear in' the yfollowing description; and

` the novel features pointed out in the appended claims. Figure 1 indicates graphically the chemical reactions performed in my invention.

Figure?! shows apparatus for effecting the rey covery of the ley-products.

' The wash Water in the vat l drainsinto the tank "zgThe initial step requires-theY addition of 0.90 lb. offsodium hydroxide (NaOH) per l gallon of the corrosive filtrate. i This 'is placed in the mixing tank i, and While the caustic soda is added the agitator 2 in the tank is continually operating. The filtrate from the tank then passes thru a continuous filter indicated at`3, to separate and retain the lter cake, which, after being properly Washed with water and then heated, becomes the lay-product iron oxide (Fe2O3) The lter cake of Yiron oxide (l'e2O3) is washed in a vat 'i tovvhieh water is added and the mass agitated. The resultant iron hydroxide Fe OH a is heated to produce iron oxide (Fe203) and Water.

4 and the calcium oxide (CaO) is supplied to the tank 4 through a pipe 8.

The liquid filtrate from the lter 3 passes into the mixing tank fi containing an agitator 5, Here the addition of calciurn'oxide or quick lime (0.36 l

lb. of CaO) per 1 gallon is made. The lter 6 retains the calcium sulphate (CaSO4-2H2O),

which can readily be converted into plaster of f Paris (CaSO4-1/2H2O) by heating. The liquid filtrate leaving the iilter 6 contains a predominant percentage of sodium hydroxide (NaOH), which is recycled back into the tank I; and after the operation becomes continuous, less than 10% of the original quantity of sodium hydroxide (NaOH) needs to be added to make up the loss sustained in the original chemical reaction. On this basis the recovery of commercial 1any-products per 1 gallon of the corrosive filtrate will be approximately as follows: l1/2 ounces of iron oxide (FezOs) and 2 lbs. of calcium sulphate (CaSOi-2l-l20), and the entire waste eluent is completely neutralized.

Figure 1 demonstrates that the sodium hydroxide (NaOH) solution may be recycled once or several times, into the tank I; thereby neces- A sitating relatively small amounts of fresh charges of sodium hydroxide into "this tank. In any event, when excessive amounts of this solution becomes available, a portion, or all of it may be converted by treatment with carbon dioxide (CO2) (see Figure 2), into either anhydrous sodium carbonate (NazCOa), of such forms as Na2CO3-2I-I2O, or Na2CO3.101-I2O, all depending upon how far down the sodium salts are dried. The yield of anhydrous sodium carbonate (NazCOa), will amount to 1.11 lbs.; or instead of this byproduct, I can obtain a yield of 3.22 lbs. of carbonate or the composition NazCOalOHzO, which is an essential alkali for soap making.

A second alternate within the scope of this invention is that a portion of the sodium hydroxide NaOH solution will be recycled as shown in Figure 1; and the remainder of the strong sodium hydroxide solution will be neutralized with a low grade hydrochloric acid (HC1), (not shown in illustration) which will form common sodium (NaCl) chloride. This may be readily discharged into streams without polluting them, especially the sea. Thus a cheap and safe meth- .od of disposing of the excess sodium hydroxide is realized.

While the foregoing specication discloses my invention fully, I do not wish to be limited to the exact details of procedure stated, but reserve the right to adopt variations which do not depart from the principle of the invention.

For example, calcium or potassium hydroxides could be used instead of sodium hydroxide in all of the above-mentioned results obtained thereby in the performance of the process of this invention. The improvement is particularly valuable in the recovery and neutralization of waste ltrates resulting from the manufacture of titanium dioxide.

Having described my invention, what I believe to be new is:

1. The process of treating liquid industrial waste containing sulphuric acid and ferrous sulphate, consisting in adding sodium hydroxide in suiiicient quantity to neutralize the acid to the liquid and agitating the mixture, iiltering and removing the iron hydroxide iilter cake, heating the latter to form iron oxide and Water. adding oxide of lime to the liquid filtrate in suiiicient quantity to convert the iiltrate into a liquid mixture of calcium sulphate and sodium hydroxide and agitating the mixture, filtering said last-named mixture to remove the calcium sulphate, returning part of the sodium hydroxide 'in said last-named mixture to replenish the sodium hydroxide originally used, and treating the remainder of the second filtrate with heat and carbon dioxide to form sodium carbonate.

.2. The process of treating liquid industrial waste according to claim 1 wherein approximately 0.9 lb. of sodium hydroxide is first added to each gallon of said liquid waste; and approximately 0.36 of oxide if lime is utilized with each gallon of liquid ltrate to produce sodium hydroxide and calcium sulphate.

3. The process of treating liquid industrial waste according to claim 2 wherein approximately 0.9 lb. of sodium hydroxide is iirst added to each gallon of said liquid waste; and approximately 0.36 of oxide if lime is utilized with each gallon of liquid filtrate to produce sodium hydroxide and calcium sulphate, and the firstnamed iilter cake is washed with water, which is afterwards discharged into the second-named mixture.

ANTHONY L. NUGEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 53,839 Lahrnann Apr. 10, 1866 708,585 Ramage Sept. 9, 1902 802,928 Fireman Oct. 24, 1905 1,254,009 Hughes Jan. 15, 1918 1,547,624 Smith et al. July 28, 1925 1,596,363 Mac Millan Aug. 17, 1926 1,637,514 Bradley Aug. 2, 1927 2,072,177 Moore Mar. 2, 1937 2,258,310 Abbott Oct. 7, 1941 2,271,524 Marek Feb. 3, 1942 

1. THE PROCESS OF TREATING LIQUID INDUSTRIAL WASTE CONTAINING SULPHURIC ACID AND FERROUS SULPHATE, CONSISTING IN ADDING SODIUM HYDROXIDE IN SUFFICIENT QUANTITY OF NEUTRALIZE THE ACID TO THE LIQUID AND AGITATING THE MIXTURE, FILTERING AND REMOVING THE IRON HYDROXIDE FILTERCAKE, HEATING THE LATTER TO FORM IRON OXIDE AND WATER, ADDING OXIDE OF LIME TO THE LIQUID FILTRATE I SUFFICIENT QUANTITY TO CONVERT THE FILTRATE INTO A LIQUID MIXTURE OF CALCIUM SULPHAT AND SODIUM HYDROXIDE AND AGITATING THE MIXTURE, FILTERING SAID LAST-NAMED MIXTURE TO REMOVE THE CALCIUM SULPHATE, RETURNING PART OF THE SODIUM HYDROXIDE IN SAID LAST-NAMED MIXTURE TO REPLENISH THE SODIUM HYDROXIDE ORIGINALLY USED, AND TREATING THE REMAINDER OF THE SECOND FILTRATE WITH HEAT AND CARBON DIOXIDE TO FORM SODIUM CARBONATE. 